The value of maintenance neuroleptic treatment in outpatient schizophrenics has been well established. Research must now be directed towards maximizing benefits and minimizing risks of long-term chemotherapy by determining the lowest effective dosages for prevention of relapse. This study compares "low dose" neuroleptics - fluphenazine decanoate 1.25 mg to 5.0 mg bi-weekly to "standard dose" - fluphenazine decanoate 12.5 mg to 50 mg bi-weekly in remitted or clinically stable schizophrenics attending an aftercare clinic. The study period for each patient is one year. The expected sample is 50 patients in each treatment group. The study is double-blind and the entire project will take 3 to 4 years. Outcome measures include subjective and objective ratings of symptomatology, relapse rates, ability to be restabilized following relapse, extrapyramidal side effects, early signs of tardive dyskinesia (and long-term follow-up for tardive dyskinesia), social adjustment and family burden. In addition, serial measures of fluphenazine blood levels and serum prolactin are being carried out with the hope of developing objective measures for identifying minimum effective dosage requirements in this context.